1. Field of the Invention
The present invention relates generally to head assemblies including rotating head systems and the like. In particular aspects, the invention relates to methods and devices for sealing a rotating drilling head or other device having a rotatable bearing against a drill pipe or other tubular member.
2. Description of the Related Art
Rotating drilling head systems use an elastomeric element to seal the drilling head against a drill pipe during drilling operations. One of such systems is described in U.S. Pat. No. 6,016,880, entitled xe2x80x9cRotating Drilling Head with Spaced Apart Seals,xe2x80x9d which has been assigned to the assignee of the present invention. That patent is incorporated herein by reference. Rotating drilling head arrangements typically use a cartridge unit that can be readily installed and removed from a housing for replacement of the elastomeric elements.
The cartridge unit for the system of the ""880 patent is landed within a housing that contains several laterally oriented fluid flow ports through which lubricating fluid is pumped. The fluid ports on the housing are aligned with complimentary ports in the cartridge unit to form complete flow paths. The flow ports are sealed from one another using smaller diameter seals, each concentric with one of the flow ports. Unfortunately, if small diameter seals are used, they wear out quickly as replacements of the cartridge occur.
Gallery seals work better than the small diameter elastomeric seals. However, to work properly, there must be stepped increases in the diameter of the main housing within which the cartridge unit resides. Too many of these diameter increases result in the cartridge unit being too large at the upper end, thereby requiring a larger main housing, which may be impractical. A cartridge unit and drilling string of smaller diameter can be used instead. However, this is generally considered to be undesirable as drilling productivity is reduced.
The present invention addresses the problems of the prior art.
The invention relates generally to head assemblies and like devices wherein there is an outer housing that carries a cartridge assembly that permits rotational movement. In particular aspects, the invention provides techniques for establishing an improved seal between the outer housing and the cartridge assembly. Additionally, the invention provides techniques for improved lubrication of the bearings used within the cartridge assembly. An exemplary rotating drilling head assembly is described that is representative of this type a head assembly and includes a cartridge assembly made up of a cartridge housing and cartridge body that is rotatable within the cartridge housing. In the preferred embodiment described, static seals are used to provide fluid seals between the radially outer surface of the cartridge housing and the outer housing. On or more fluid passages within the cartridge housing carry lubricating fluid from the static seals to dynamic seals that allow the cartridge body to rotate easily within the cartridge housing. One or more fluid passages and static seals are also provided so that spent fluid may be removed through the cartridge housing.
The static seal arrangement of the present invention is advantageous, as compared to prior art techniques for providing sealing in these types of head assemblies. For example, there may be multiple fluid inlets and outlets within the cartridge housing without requiring a multiplicity of stepped increases in the diameter of the cartridge housing and the outer housing. Instead, the inlets and outlets are angularly spaced about the circumference of the cartridge, and the fluid passages extend axially through the cartridge housing to a different axial position, or elevation, along the body of the cartridge housing. The static seals also provide resilient and lasting fluid sealing.